1. Field of the Invention
The present invention relates to a light emitting device and a method of driving the same. More particularly, the present invention relates to a light emitting device where currents passing through scan lines have the same values and a method of driving the same.
2. Description of the Related Art
A light emitting device emits a light having a certain wavelength, and especially an organic electroluminescent device is self light emitting device.
FIG. 1A is a block diagram illustrating a common organic electroluminescent device. FIG. 1B and FIG. 1C are views illustrating a method of driving the organic electroluminescent device of FIG. 1A.
In FIG. 1A, the organic electroluminescent device includes a panel 100, a controller 102, a first scan driving circuit 104, a second scan driving circuit 106 and a data driving circuit 108.
The panel 100 includes a plurality of pixels E11 to E34 formed in cross areas of data lines D1 to D3 and scan lines S1 to S4.
The controller 102 controls the scan driving circuits 104 and 106 and the data driving circuit 108 by using display data inputted from an outside apparatus (not shown).
The first scan driving circuit 104 is coupled to some of the scan lines S1 to S4, e.g. S1 and S3, and transmits first scan signals to the some S1 and S3.
The second scan driving circuit 106 is coupled to the other scan lines S2 and S4, and transmits second scan signals to the other scan lines S2 and S4.
The data driving circuit 108 provides data currents corresponding to the display data to the data lines D1 to D3 under control of the controller 102, and so the pixels E11 to E34 emit a light.
Hereinafter, a process of driving the organic electroluminescent device will be described in detail with reference to FIG. 1B and FIG. 1C. Here, the pixels E11 to E34 emit a light when corresponding scan line is coupled to a ground, and do not emit a light when corresponding scan line is coupled to a non-luminescent source having the same magnitude as a driving voltage of the organic electroluminescent device, e.g. a voltage V1 corresponding to maximum brightness of pixel. In addition, data current of 0 A is provided to a pixel E11 through a first data line D1, and data currents of 3 A are provided to the other pixels E12 to E34. Additionally, resistor (hereinafter, referred to as “scan line resistor”) which each of the scan lines S1 to S4 has is assumed by 10Ω.
In FIG. 1B, the first scan line S1 is coupled to the ground, and the second to fourth scan lines S2 to S4 are coupled to the non-luminescent source. Accordingly, pixels E21 and E31 of the pixels E11 to E31 corresponding to the first scan line S1 emit a light. In this case, a first current passing to the ground through the first scan line S1 is 6A. Hence, each of cathode voltages VC21 and VC31 of the pixels E21 and E31 is 60V (scan line resistor×6 A).
In FIG. 1C, the second scan line S2 is coupled to the ground, and the first, third and fourth scan lines S1, S3 and S4 are coupled to the non-luminescent source. Accordingly, pixels E12 to E32 corresponding to the second scan line S2 emit a light. In this case, a second current passing to the ground through the second scan line S2 is 9A. Hence, each of cathode voltages VC12 to VC32 of the pixels E12 to E32 is 90V (scan line resistor×9 A).
Hereinafter, the pixel E21 corresponding to the first scan line S1 and the pixel E22 corresponding to the second scan line S2 will be compared.
As described above, though data currents having the same magnitude are provided to the pixels E21 and E22, the cathode voltage VC21 and VC22 of the pixels E21 and E22 have different magnitude. Here, the brightness of a pixel is affected by cathode voltage of the pixel, and thus the pixels E21 and E22 emit light having different brightness. Generally, the higher cathode voltage of a pixel has magnitude, the lower the pixel has brightness. Accordingly, the pixel E21 emits a light having higher brightness than the pixel E22.
In case of the pixels E31 to E32, the cathode voltages VC31 and VC32 of the pixels E31 and E32 are different magnitude, and so the pixels E31 and E32 emit light having different brightness. This is referred to as “cross-talk phenomenon”.